1. Field of the Invention
This invention relates to a system and a method for semiconductor processing process control, and more particularly, to a semiconductor processing process control system capable of flexibly, quickly coping with changes in processing process, method of computing control variables and processing equipment, and its control method.
2. Description of the Related Background Art
For manufacturing semiconductor devices such as IC, LSI, and so on, they undergo many processes like etching, cleansing, inspection, and others, and intended processing is conducted in each process. For realizing intended processing, control conditions each processing apparatus and its processing time must be adjusted appropriately.
For example, in case of stacking a film in a certain process, material of the film (film material) and its thickness are targets of the processing. The content of this processing is to make a film of an intended material on a specific semiconductor. Only when control conditions of the deposition apparatus (in case of a CVD apparatus, the are conditions on the material of the gas, flow rate of the gas, temperature, etc.) are selected properly, the intended content of the processing (making a film of an intended material) can be realized, and the film thickness can be controlled by adjusting the duration of time of the deposition (deposition time). The deposition time can be obtained by dividing the target film thickness by the deposition rate (film thickness stacked in a unit time, namely, a kind of processing speed). Such deposition rates are previously measured upon maintenance of the apparatus, for example, and held in form of a rate table.
When etching processing is conducted, the content of the processing is to etch a film of a specific material stacked on a specific semiconductor, and this processing content and the etching depth (film thickness) are the target of the processing. To realize this content of the processing, control conditions of an etching apparatus are determined. Further, the etching time (processing time) is determined by dividing the target etching depth (thickness) by the etching rate (etching depth in each unit time, i.e., a kind of processing speed). Such etching rates are held as a rate table similarly to the case of deposition of films.
To supervise control conditions of processing apparatuses and processing times in a plurality of processes, a semiconductor processing process control system is used. Taking here deposition of a film (as a single process) as an example of processing content, a flow of process control by a conventional semiconductor processing process control system is shown. The process flow is shown in FIG. 29, and the flow of process control is shown in FIG. 30.
As shown in FIG. 30, a semiconductor processing process control system CS1 reads out the processing target (in this case, material and thickness of the film to be stacked) of the process and control conditions of a processing apparatus from process flow information IF1. Then, the semiconductor processing process control system CS1 obtains the processing time (in this case, deposition time) by referring to a rate table RT1 and dividing the target film thickness by the deposition rate. In this example, 100 minutes obtained by dividing 1000 angstrom as the target film thickness by 10 angstrom/min. as the deposition rate is the deposition time. Then, it sends the control variables (setting of conditions concerning control of the processing apparatus involving both control conditions of the processing apparatus and its processing time, also in the description made hereunder) to the processing apparatus PA1 like a deposition apparatus or its control device, for example. In the example shown in FIG. 30, the control method for the target process is a fixed method.
FIGS. 31 and 32 show method of computing the processing time upon stacking a plurality of films and the processing time upon etching a plurality of films. In this case, since control conditions and processing speed (deposition rate, etching rate, etc.) of the processing apparatus PA1 vary with materials of films to be stacked or etched, processing time must be calculated for each step for processing each film.
The semiconductor processing process control system CS1 may be made up of hardware alone. Normally, however, it can be made as programs on a computer (software) to ensure quick response to changes in process, etc. This is shown in FIG. 33.
As shown in FIG. 33, there are process control programs CPG for respective processing apparatuses PA1 through PA4 used for respective processes, and these programs control the processing apparatuses PA1 through PA4. That is, a set of a plurality of process control programs CPG realizes the function of the semiconductor processing process control system CS1. When the process and the apparatus there for are changed from one to another, the system can copes with it by changing the content of the respective process control programs CPG.
However, there is the problem that control conditions are not fixed ones determined only by processing apparatuses PA1 through PA4 and processing contents and deposition rate is not always constant.
That is, control conditions are variable with the history of use of each processing apparatus. Additionally, deposition rate may change depending on the status of the base on which a target film should be stacked. Therefore, it is possible that the deposition rate varies with thickness of the stacked film.
As a method dealing with this problem, Japanese Patent Laid-Open Publication No. hei 8-45804 discloses a method for computing appropriate control conditions taking the past control conditions into consideration, and Japanese Patent Laid-Open Publication No. hei 6-196404 discloses a method for computing a processing time from a target film thickness.
These methods for computing control conditions and processing time are not always fixed but may vary with target processing contents and other factors. Conventional semiconductor processing process control systems, however, could not flexibly cope with changes in calculation method of control conditions and processing time, and were compelled to re-make the whole program every time upon changing the calculation method.
Furthermore, conventional systems involved the problem that they needed a change of the whole program also upon every change of the processing apparatus and process (not only a change of the process from one to another, but also omission and addition of a step).
As explained above, conventional semiconductor processing process control systems could not quickly cope with changes in process, calculation method of control variables, processing apparatus, and so on, and as a result, there was the possibility of delaying development of semiconductor devices.